Electric heating unit.



H. G. WEEKS.

ELECTRIC HEATING UNIT. APPLICATION FILED JAN. 10, 1912.

1,169,213. Patented Jan.25, 1916.

I Y $2M) rinirnn STTEs Pag NT FFTCE.

HARRY G. \VEEKS, CHICAGO. ILLINOIS, ASSIGNOR T FREDERICK C. AUSTIN, OF

CHICAGO, ILLINOIS.

ELECTRIC HEATING UNIT.

Specification of Letters Extent.

Patented Jan. 25, 1916.

Application filed January 10, 1912. Serial No. 670,418.

' citizen of the United States of America, and

resident of Chicago, \Cook county,'lllinois,

have invented a certain new and useful Improvement in Electric Heating Units, pf which the following is a specification.

My invention relates to electric heating devices in general, such, for example, as stoves and flat irons and other similar devices.

It relates more particularly to the heating unit or resistance employed in devices of this kind.

Generally stated, the object of my invention is to provide an improved and highly efficient construction and arrangement of the heating unit or resistance of an electric heating device.

Special objects are to. provide a novel and efficient form of metallic heating unit of such character that it is practically selfinsulating by reason of the natural oxid which forms on the surface thereof; to provide a heating unit rendered flat in a novel and etiicient manner; to provide a novel and effective arrangement whereby aifieret degrees of heat may be produced at will; to provide a novel arrangement of the heating unit whereby one pilot lamp is sufficient for the three degrees of heat; and toprovide certain details and combinations tending to increase the general efiiciency of the heating unit of a device of this particular character.

To the foregoing and. other useful ends,

set forth and claimed.

In the accompanying drawingsFigure 1 is a diagram indicating a fiat iron provided with a fiat heating unit embodying the principles of my invention. Fig. 2 shows the method of forming the coil on a mandrel. Fig.- 3 is an endview of said coil before being flattened. Fig. t shows the method of flattening the coil by rolling the convolutions thereof over upon each. other. Fig. 5 is an edge view of a portion of the completed coil or heating unit.

As thus illustrated, and referring more particularly to Figsl to 5, inclusive, my invention comprises a heating unit A having convolutions a that lean over and rest upon each other-that is to say, overlap each other. The result'of the formation is that with each ot er.

the said relatively displaced convolutions have parallel axes that extend crosswise of the length of the flattened unit produced thereby. The said heating unit is preferably, and as a mattervof further and special improvement, made of the metal called nicrome. I have discovered that by the use of this metal the convolutions of a coil may be crowded tightly together, and may thus be in engagement with each other, without short-circuiting. This is for the reason that nicrome oxidizes and provides itself with a thin coating that serves as efi'ective insulation. A thus constructed may be made in various Ways. As shown, the said heating unit is produced by first winding the nicrome Wire on the mandrel B, to form a helical coil with the convolutions thereof disposed about a common longitudinal axis. Then the coil is laid on a table and rolled down by a roller C, the effect being'not to crush the convolutions, but simply to tumble or lay them over upon each other, whereby the said convolutions overlap each other like the shingles of a house. The result is that the ing unit as a Whole is rendered flat and more effective in characten'but the convolutions themselves are not flattened, but simply twisted into different planes or positions. This avoids sharp bends in wire which might break the metal or weaken it and increase the resistance at certain points.- In this Way the convolutions engage each other, but the insulating oxid thereof is sufficient to prevent the current from jumping across from one convolution to another. Preferably, the conditions are such that the drop in potential from one convolution to another is not more than six volts, and where the current is maintained for sometime I find that three volts is even better. With these conditions the oxid insulation does not tend to The flat heating unit break down, even when the convolutions are tight to ether and in metallic contact As shown in Figs. 4 and 5, tlie result of the flattening operation is that the convolutions of the coil overlap each other shingle fashiomso to speak, and are not distorted by abrupt or sharp heads therein. Ali abrupt head in a wire is liable to increase the resistance at such a point, if the metal is stretched or broken or weakened by the abrupt heiul, and in that event the coil is liable to burn out more quickly, as it may heeolne overheated at the point where the resistance has been increased by the weaken-- iug oil the metal. In my improved construction, however, the coils are not subject to abrupt or sharp bends in the wire and in addition there arev no places in the coil where two portions of the wire extend parallel with each other. Thus the danger of burning out and short circuiting is retluced to a seaside able extent.

hat I claim as my invention is:-

1. An electric heating unit in the form of a coil of Wire having the convolutions in- HARRY Gr. 'WEEIKS.

llitnesscs;

time. F. Stunning E. H. Cuzco. 

